1. Field of the Invention
The present invention relates to a composition for forming an antifouling film which can form an antifouling film excellent in stain resistance and abrasion resistance on a substrate, to an optical component which has the antifouling film and is adhered to a panel surface of a CRT (cathode ray tube) etc. and used as an anti-reflection filter, and to a display device to which the optical component is adhered on a panel surface thereof.
2. Description of the Related Art
When viewing an object through a transparent material, it is troublesome if the reflected light is strong and the reflected image is clear. In, for example, a lens for eyeglasses, a reflected image referred to as a "ghost" or "flare" is produced and gives an uncomfortable feeling to the eyes. Further, in a telescope or the like, there arises a problem in that the object viewed cannot discerned due to the light reflected on the glass surface.
Conventionally, the method used for preventing the reflection has been to form a coating of a substance having a different refractive index from that of the substrate on the substrate by a vacuum deposition process or the like. In this case, it has been known that the selection of the thickness of the substance covering the substrate is important so as to make the anti-reflection effect the highest.
For example, in a single coating film, it has been known that the selection of the thickness of an optical film of a substance having a lower refractive index than that of the substrate to 1/4 of the light wavelength concerned or an odd multiple of the same gives the minimum reflection rate, that is, the maximum transmission rate.
Here, the optical film thickness is given by the product of the refractive index of the coating film forming material and the thickness of the coating film. Further, the formation of multiple anti-reflection layers is possible. Some proposals have been made concerning the selection of the film thickness in this case (Optical Technology Contact, Vol. 9, No. 8, p. 17, (1971)).
On the other hand, in Japanese Unexamined Patent Publication (Kokai) No. 58-46301, Japanese Unexamined Patent Publication (Kokai) No. 59-49501 and Japanese Unexamined Patent Publication (Kokai) No. 59-50401, a method of forming an anti-reflection film made of multiple layers satisfying the conditions of the optical film thickness by using a liquid composition has been disclosed.
In recent years, optical products having an anti-reflection property have been devised using a plastic film as a substrate actively utilizing the advantages thereof such as the light weight, safety, and ease of handling and have been commercialized by the method of adhering the same as an anti-reflection filter to the panel surface of a CRT etc. In many of them, use has been made of an inorganic oxide film represented by silicon dioxide or an inorganic halide film.
In the anti-reflection film formed by the vacuum deposition process or a sputtering process, the coating film forming material is mainly comprised of an inorganic oxide or inorganic halide, therefore the anti-reflection film essentially had a high surface hardness, but had drawbacks that stains due to finger marks, sweat, or cosmetic agents such as hair liquids and hair sprays were apt to be remarkable. It was also hard to remove these adhered stains. Further, since the slipperiness of the surface was poor, there was the problem that a scratch formed when it came into contact with a some hard object or another became wider etc. Further, since the wetting property with respect to water was large, there was the problem that when drops of rain and splashes of water were adhered, they largely expanded. In eyeglass lenses etc., the object viewed seemed to be distorted over a large area.
In the anti-reflection film disclosed in Japanese Unexamined Patent Publication (Kokai) No. 58-46301, Japanese Unexamined Patent Publication (Kokai) No. 59-49501, and Japanese Unexamined Patent Publication (Kokai) No. 59-50401 as well, in order to impart a high surface hardness, it is necessary to include at least 30 percent by weight of an inorganic substance such as fine silica particles in the outermost surface film, but the anti-reflection film obtained from such a film composition has problems that the surface slipperiness is poor and scratches are easily caused due to rubbing by cloth etc.
Various surface treatment agents have been proposed so as to solve these problems and are commercially available, but all of them are dissolved by water or various solvents, give their function only temporarily, are not permanent, and thus are poor in durability. Further, Japanese Unexamined Patent Publication (Kokai) No. 3-266801 reports the formation of a fluorine-based resin layer due to imparting of the volatility. However, although the volatility was indeed increased by these fluorine-based resins, satisfactory results with respect to the friction or abrasion could not be obtained.